Car battery was flat at Xmas, used the jump leads,started no bother, bought a second hand battery that came out of a 2015 Audi, stuck it in no ignition lights ,not starting, tried to jump start with leads no joy no ignition lights , not starting, put back in original battery and connected jump leads ,no ignition lights, not starting, bought a brand new battery, same problem no ignition lights,not starting 

The battery might have had to be programmed to the car. 

I think u r right, had a mechanic down last week and plugged in to computer, not Audi software but car will not communicate with computer, no lights on ignition when u turn key, completely dead, head lights ,central locking all works 

Definitely get the battery coded. 

It is a varta  battery that was in the car before, don’t see a bem code, the new battery I bought is monbat is the name of it, I bought it out of a car accessorie shop, they put registration into computer a gave me the battery, although it’s a bit small that the original, does it still have to be coded , don’t see a code on it either, would it still cause no ignition lights, when u turn the key in ignition it doesn’t make the sucking sound

39 minutes ago, Paddy38 said:

It is a varta  battery that was in the car before, don’t see a bem code, the new battery I bought is monbat is the name of it, I bought it out of a car accessorie shop, they put registration into computer a gave me the battery, although it’s a bit small that the original, does it still have to be coded , don’t see a code on it either, would it still cause no ignition lights, when u turn the key in ignition it doesn’t make the sucking sound

Hi sorry to be the bearer of bad news but you will need the BEM code from the top of the original battery to code the new one, you have to have VCDS or OBD Eleven to code it there is a video on youtube about how to code the battery using the old code but you have to change one digit of the code so it thinks thats the proper new battery, fitting a smaller battery is no good as the dimensions and amp hour/cranking voltage has to be exactly the same as the old unit, my guess is that the 2015 battery was an AGM for stop start which runs totally different voltage when cranking and I think you have probably fried the BEM module.

Steve.

Hi Steve, I have the original battery here at home, ur right about the second hand battery, it was start stop, when I put the start stop battery in ,it wouldn’t crank, no ignition lights at all,just dead, does this mean I still fried the bem module 

23 hours ago, Paddy38 said:

Hi Steve, I have the original battery here at home, ur right about the second hand battery, it was start stop, when I put the start stop battery in ,it wouldn’t crank, no ignition lights at all,just dead, does this mean I still fried the bem module 

Hi its quite possible as the electrics on these cars don't like voltage spikes, fortunately from memory I think the BEM is on the earth lead on the battery and is fairly cheap/easy to replace, have a look on youtube I remember watching a couple of videos on how to change the BEM.

Steve.

Thanks very much for ur help

Hello, how did you resolve your issue with no ignition, same problem here, got an Audi q7 etron diesel, was loaded fine on trailer and when it arrived it can not be powered up, the battery is charged up but ignition wouldn't appear on push of the start button. lock and unlock works.